(1) Field to which invention relates
The invention relates to an electrolytic cell for the treatment of water, more particularly for the purification and sterilization of water; it relates in particular to a multipole electrolytic cell, which can be used in the most varied fashions for the treatment, and more particularly for the purification and sterilization of water, and comprises a closed container with a lower inlet opening and an upper outlet opening for the water and at least two electrodes within the container, which are adapted to be connected with the positive and negative pole of a DC source.
(2) The prior art
The most varied types of electrolytic cells for the treatment, and more particularly for the purification and sterilization of water, have been proposed. With these known cells it is possible to remove the dissolved and suspended contaminating materials comprised in the water to be treated electrolytically by using either consumble or not-consumable electrodes of iron, aluminum, copper, silver, platinum, carbon etc. However, during operation of such electrolytic cells many problems are encountered which are due to different causes.
Normally during electrolysis of water, especially of hard water, the cathode is rapidly covered by a skin of calcium carbonate which inhibits the flow of current; anodes of silver, copper, iron, aluminum etc. during the electrolysis are covered with oxide films. In case of aluminum anodes the formed aluminum oxide prevents the flow of current. In the case of silver, iron and copper anodes the formed oxide film is highly conductive, so that the dissolution of the metal is prevented and oxygen is produced at the electrodes.
Another problem encountered in electrolytical water purification systems is that the water normally encountered has only a very small number of ions and that, although platinum anodes can provide oxidation, the oxidation-reduction potential of the water remains very low. E.g., if chloride is to be produced, the chloride concentration in the water must be very high and this concentration is normally not encountered in fresh water, particularly drinking water.
The standard electrolytical technique to chlorinate water in swimming-pools is to provide a separate cell containing a high concentration of common salt which upon electrolysis gives sodium hypochlorite or chlorine which is fed into the swimming-pool. Theoretically, it is possible to add sufficient common salt to the swimming-pool water and to electrolyze it directly. However, this technique has the disadvantage that the water tastes salty to the bathers and that the calcium contained in the water deposits onto the cathodes to such an extent that the flow of the current stops. Changing of polarity to remove the calcium deposits on the cathodes has been found in practice only to lead to corrosion of the cathode and aggravates the problem.